1. Technical Field of the Invention
This invention relates generally to coded image capture and decoding, and, more particularly, to a coded image capture and decoding system having capture processing circuitry for capturing a plurality of images, and having host processing circuitry which manages, among many other processing tasks, the decoding of the images. The capture processing circuitry operates to prevent the host processing circuitry from having to dedicate itself in real-time to the decode processing of incoming captured coded images from the capture processing circuitry, permitting the host processing circuitry to be shared by other hardware and/or software for performing other often real-time tasks. In addition, the capture processing circuitry functionality also permits both the host and capture processing circuitry to achieve enhanced power conservation performance.
2. Description of Related Art
As is well known, optical targets, such as a bar code label, can be found on goods or articles for tracking or accounting purposes, for example. Each of the optical targets contain coded information which either directly provides information about the good or article marked with the optical target, or indirectly provides such information with the assistance of cross-reference databases. For example, the target may only contain an alphanumeric sequence that a cross-referenced database uses to identify details regarding the good or article marked with the target such as the type of good, destination, cost, manufacturer, etc.
Conventional coded image capture and decoding systems sequentially capture images of coded optical targets, and attempt to decode each image as it is captured. If a first image is successfully decoded, the capturing process ends. Otherwise, another image is captured for a further decode attempt. Typically, this sequence continues until either a coded image is successfully decoded, or a predefined number of failed decode attempts occurs. Upon successfully decoding a coded image, the decoded data is often compared to a cross-reference database to extract further information. Such information and the decoded data are then used for specific applications such as retail checkout, package identification, tracking, shipping and accounting.
Coded targets may comprise one or two-dimensional images. A bar code label constitutes an exemplary one-dimensional coded target. Bar codes provide a robust mechanism for encoding and decoding relatively small amounts of data. Although two-dimensional coded targets typically incorporate more data than one-dimensional targets, they often prove much more difficult to decode.
Some coded image capture and decoding systems comprise both a hand-held unit and a stationary host unit. Such a configuration can be found, for example, in point-of-sale applications wherein a wand reader or low-cost, hand-held bar code reader captures and communicates coded images to a cash register host via a wired or wireless link to perform decode and subsequent processing.
In such systems, the hand-held capture unit includes optical components for assisting in the capture of coded images. For example, the optical components in a typical wand comprises a laser diode and a phototransistor detector. In a laser scanning reader, the optical assembly might also comprise scanning motors, mirrors and lens assemblies. Similarly, for continuous or flash type readers, the optical components might comprise photodetector arrays, lens systems, mirrors and flash or LED (light emitting diode) light sources. In addition, the hand-held capture units of such systems typically contain image processing and interface circuitry for communicating each coded image to the stationary host unit for attempts at decode processing.
Other coded image capture and decoding systems comprise battery powered portable units and include both coded image capture and decode functionality. In addition to performing capture and decode functionality, such portable units often perform tracking, inventory, data processing, communication functions, etc. Typically, the portable units require a high performance host processor that performs the image decoding functions as well as other hardware and software functions. The high performance host processor, as well as the associated support circuitry, consumes significant power during its operation and quickly drains the battery powering a portable unit. Some portable units that capture and decode two-dimensional codes also require high power consuming digital signal processors for decoding functions, causing the units to have limited battery life.
In operation of such systems, a read cycle is typically initiated by pushing a button, pulling a trigger or through proximity detection of a coded image within reading range. Upon initiation of a read cycle, the system delivers light, such as a scanned laser beam, LED or xenon flash, for example, to a coded target. A photodetector means of the system receives reflections from the coded target, capturing the reflected image (hereinafter a “coded image”). Interface circuitry delivers the coded image from the photodetector to a waiting host processor. Typical photodetector means include a single or plural phototransistors or phototransistor (CCD) arrays, for example.
The capturing of a coded image often occurs at a relatively slow rate in relation to typical host processor execution times. For example, laser type scanning systems scan a laser beam across a coded target at relatively slow scan rate to provide sufficient exposure time for photodetector sensing. Optical units that include an array of photosensitive elements typically require relatively long exposure times, and slowly produce image data sequentially after a target is read. Optical units also often include lenses that must be adjusted to focus on the target to capture valid image. Lens adjustments also occur relatively slowly. Because coded images are produced no faster than the rate the image data is received, coded images are typically transmitted to the host processor at a much slower rate than the fastest decode rate achievable by the host processor.
Thus, the host processor in conventional systems remains in a dedicated mode waiting for then attempting to decode each image as it is captured until one of the images is successfully decoded. During this time, the host processor is not able to conduct other types of processing or enter a worthwhile power saving state. Because some other types of processing often require real time dedication as well, additional dedicated processors or processing circuitry often proves necessary even though cost and power consumption increase.
Thus there is a need in the art for a reduced power, coded image capture and decoding system that solves the foregoing and other problems that will become apparent in view of the drawings and remainder of the specification which follows.